A window frame consists of side jambs interconnected by a head and a bottom sill. The side jambs include tracks through which sashes move as the window opens and closes. The side jambs may also include a track for a window screen.
The fames are designed and constructed to inhibit the intrusion of water into the interior of the building into which the frame is installed. Accordingly, to direct water away from the building, the bottom sills in known prior assemblies are often vented or sloped and/or include stepped inserts. Water infiltration through the head sill is not generally a problem, and thus, the top, or head, is not typically vented, sloped or stepped.
The window frame must be carefully assembled, to avoid, as much as possible, openings through which water can enter and accumulate in the frame itself and/or seep from the frame into the interior of the building. The difficulty is that the side jambs and the bottom sill have shapes that are essentially incompatible.
To facilitate attachment of the side jambs and the bottom sill, the jambs in prior known assemblies consist of two or more detachable sections, namely, a base shaped to mate with the sill and one or more inserts that form the tracks. Either the base or the inserts must include openings into which tabs on the other fit to hold the sections together. Such a frame is constructed by connecting the jamb bases to at least the bottom the sill by, for example, welding them together at the corners. The inserts for the tracks are then attached to the bases. The ends of the inserts are thus not affixed to the bottom sill. While such an assembly is relatively water tight, water may enter the assembly either through the openings for receiving the inserts or the openings between the ends of the inserts and the bottom sill.
Constructing these prior known frames is labor intensive, requiring the series of welding and assembly steps discussed above. The bottom sill may also require assembly, if it includes stepped inserts. Such labor intensive assembly processes are expensive, increasing the cost of the assembly. Manufacturing the various sections of the jamb is also costly, since the inserts and the base must be separately produced.